High speed rotation or other high speed movement of metal parts relative to each other requires substantial lubrication therebetween. For example, the steel shafts which carry cotton pickers at their outer ends are rotated at very high speeds within bronze bushings. Because of the differences in the coefficients of expansion of steel and brass, certain tolerances are required to compensate therefor and lubrication is provided to minimize friction and the attendant generation of heat and undue wear. Because of such tolerances, the lubrication escapes between the bronze bushing and the shaft, as the adjacent parts of different metals heat and cool because of such high speed relative movement.
The usual attempted remedy to prevent such escape of lubricant is to apply an elastomeric sealing ring at the end of or within the bushing, but the high speed rotation quickly causes undue friction, heat and wear, and consequent destruction of the ring. Each cotton picking machine may carry as many as 1920 high-speed rotating shafts with cotton-picking devices at their outer end. Experience has shown that despite filling the gear box housing with eight (8) gallons of grease every ten (10) hours, after 11/2 hours of operation of the machine, such high-speed shafts are operating within their bushings under essentially dry conditions. In other words, substantially all of the lubricant has been lost and the machine is operating under adverse and unsatisfactory conditions, causing excessive wear. This is just one example of wear problems which exist with respect to machines using high speed rotating shafts.
No satisfactory solution has heretofore been found for the above problems. As a consequence, the heavy loss of lubricant from such machines is costly and environmentally damaging. Equally as important is the excessive wear which it causes in the machines, with consequent costly down time, delay and undue repair and expense. The high speed rotation of the shaft quickly generates excessive friction and heat between the shaft and sealing ring so that the latter wears excessively or is destroyed completely, with a complete loss of the sealing function. Thermal expansion of the shaft imposes additional pressure against the sealing surface of the sealing ring and thereby increases the wearing effects thereupon. Consequent variations in diameter of the shafts increases the leakage and ring wear problems and makes it impractical and virtually impossible to compensate therefor.
My new bearing assembly provides a marked improvement in ways of alleviating the above problems, in that it provides an automatically compensating seal in which the sealing ring is insulated from the rapidly moving member to prevent undue wear of the ring and the assembly is constructed so as to automatically adjust to variations in the shaft diameter and to effectively complete the seal thereround despite such variations.